GRAPHENE

Graphene, which consists of a single atomic sheet of conjugated sp2 carbon atoms, is rapidly becoming a rising star of materials science, physics, and chemistry because of its many intrinsic properties. A list of production techniques have been developed to enable graphene’s use in commercial applications. In general, graphene can be synthesized via two strategies: a bottom-up approach and top-down method. The bottom-up approach involves chemical vapor deposition (CVD). Although it can produce a high quality synthetic graphene, it has significant drawbacks that include a tedious manufacturing process, high manufacturing costs, and quality control issues. Top-down methods have also been used to produce graphene, for example, by exfoliation of graphite into acid-oxidized graphite oxide (GO), followed by chemical reduction of GO. However, GO has poor quality and requires reduction, which has a limited conversion to reduced graphene oxide (rGO). Hence, the original graphene structure from GO cannot be efficiently restored. In our lab, we have researched a new approach to chemical exfoliation of graphite by grafting organic molecular wedges to the defect sites (mostly sp2C–H) located mainly on the edges of graphite via electrophilic substitution reaction under mild conditions. Edge-selectively functionalized graphite (EFG) without damage to the basal plane can be produced with a simple one-pot reaction. The EFG approach is a scalable method for the cost-effective production of high-quality graphene.

Moreover, we recently developed a new approach for scalable production of graphene nanoplatelets (GnPs), which involves simple but efficient production via mechanochemical ball-milling graphite in the presence of corresponding reactants. High-speed ball-milling generates enough kinetic energy to crack graphitic C–C bonds, to induce edge reaction, to delaminate graphitic layers, and thus to yield edge-selectively functionalized graphene nanoplatelets (EFGnPs). Large quantities of EFGnPs could be efficiently prepared by mechanochemical ball-milling. Due to the minimal distortion of the graphitic basal area, EFGnPs have high crystallinity and show excellent performance in a number of applications (e.g., fuel cells, solar cells, Li-ion batteries, and flame retardants. In addition, a variety of functional groups and/or heteroatoms can be selectively introduced at the edges for different applications. Hence, this EFGnPs approach may thoroughly satisfy diverse demands and overcome previous obstacles to commercialization. We believe that this process could revitalize graphene research for practical applications (e.g., polymer composites, energy conversion and storage, flame retardants, conductive inks) and thus enable graphene to take an actual leading position as a next-generation material in future science and technology.